/*

 * Licensed to the Apache Software Foundation (ASF) under one

 * or more contributor license agreements.  See the NOTICE file

 * distributed with this work for additional information

 * regarding copyright ownership.  The ASF licenses this file

 * to you under the Apache License, Version 2.0 (the

 * "License"); you may not use this file except in compliance

 * with the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package com.bff.gaia.unified.sdk.extensions.sql.meta.provider.hcatalog;



import com.bff.gaia.unified.sdk.extensions.sql.UnifiedSqlTable;

import com.bff.gaia.unified.sdk.extensions.sql.meta.Table;

import com.bff.gaia.unified.sdk.extensions.sql.meta.provider.TableProvider;

import com.bff.gaia.unified.sdk.io.hcatalog.HCatalogUnifiedSchema;



import javax.annotation.Nullable;

import java.io.Serializable;

import java.util.HashMap;

import java.util.Map;

import java.util.Set;



/**

 * Table provider that represents a schema stored in Hive Metastore.

 *

 * <p>Supports only 'db.table' format at the moment, does not support 'catalog.db.table'.

 *

 * <p>Delegates to sub-providers to get the actual table.

 *

 * <p>If only the table name is provided, then 'db' is assumed to be 'default'.

 */

public class HCatalogTableProvider implements TableProvider, Serializable {



  private HashMap<String, String> configuration;

  private transient DatabaseProvider defaultDBProvider;

  private transient HCatalogUnifiedSchema metastoreSchema;



  private HCatalogTableProvider(

      HashMap<String, String> configuration,

      HCatalogUnifiedSchema metastoreSchema,

      DatabaseProvider defaultDBProvider) {

    this.configuration = configuration;

    this.defaultDBProvider = defaultDBProvider;

    this.metastoreSchema = metastoreSchema;

  }



  public static HCatalogTableProvider create(Map<String, String> configuration) {

    HCatalogUnifiedSchema metastoreSchema = HCatalogUnifiedSchema.create(configuration);

    return new HCatalogTableProvider(

        new HashMap<>(configuration),

        metastoreSchema,

        new DatabaseProvider("default", metastoreSchema, configuration));

  }



  @Override

  public String getTableType() {

    return "hcatalog";

  }



  @Override

  public void createTable(Table table) {

    throw new UnsupportedOperationException("Creating tables in HCatalog is not supported");

  }



  @Override

  public void dropTable(String tableName) {

    throw new UnsupportedOperationException("Deleting tables in HCatalog is not supported");

  }



  @Override

  public Map<String, Table> getTables() {

    throw new UnsupportedOperationException("Extracting all tables from HCatalog is not supported");

  }



  @Nullable

  @Override

  public Table getTable(String name) {

    // Tables should have been looked up from sub-providers.

    // If we reached this then getSubProvider(name) returned null

    // meaning there's no such DB. Try to look up the table in the default DB instead.

    return defaultDBProvider.getTable(name);

  }



  @Override

  public UnifiedSqlTable buildUnifiedSqlTable(Table table) {

    // This is the same `default` DB use case similar to how `getTable()` behaves.

    // This path should only be hit if none of the sub-providers for the DBs

    // was able to find the table.

    return defaultDBProvider.buildUnifiedSqlTable(table);

  }



  @Override

  public Set<String> getSubProviders() {

    throw new UnsupportedOperationException("Listing DBs is not supported in metastore");

  }



  @Override

  public TableProvider getSubProvider(String name) {

    return metastoreSchema.hasDatabase(name)

        ? new DatabaseProvider(name, metastoreSchema, configuration)

        : null;

  }

}